Sintering mechanism



Sept. 13, 1932. v H. NEuHAUssl SINTERING MECHANISM Original Filed Aug Patented Sept. 13, 1932 UNITED STATES PATENT OFFICE HEINRICH NEUHAUSS, OF DUSSELDORF,

GERMANY, ASSIGNOB TO THE AJAX METAL VANIA smrnnrue nner-:muren Original application led August i, 1928, Serial No. 296,803. Divided and this application med September 3, 1929. Serial No. 390,082.

invention relates to mechanism suitlike surfaces.

One purpose of myl invention is to provide 5 for sintering of the lining against a mould or pattern which is afterward removed or destroyed, permitting accurate predetermination of the finished shape and surface of the sintered product.

A further purpose is to provide mechanism which will permit successive parts of the surface to be sintered to be exposed to the more intense sintering heat.

A further purpose is mechanism toperform the sintering operations under the more favorable conditions of position, space and equipment and to obtain better sintered products.

A further purpose is to perform the sintering operation in a specially prepared sintering furnace free from the limitations and difficulties of location of the place of use.

A further purpose is to provide a form about or within which products are sintered and which is firm enough to stand the pressure of the sintered product and maintain its shape and yet is yieldable enough to avoid injury to the product, interspersing material for this purpose which can be baked out or burned out.

A further purpose is to form a special backing for a sintered refractory.

Further purposes will appear in the specification and in the claims.

My drawing is intended to be largely diagrammatic, and for this reason has been distorted freely for the purpose of illustration and without any attempt to maintain a scale. It is intended to illustrate a few only of the structures and ways upon which or in or by which my invention may be carried out, those shown being selectedv primarily from the standpoint of illustration of the invention.

Figure 1 is a transverse section showing one construction byv which a cylinder or Crucible may be preformed by sintering.

Figure 2 is a section of Figure 1 on line 2-2.

Figure 3 is a longitudinal section showing a finished Crucible.

to adapt sintering' Figure 4 is a top plan view of a form within which a special brick may be sinter'ed.

Figure 5 is a section of Figure 4e upon the line 5-5.

Figure 6 is a fragmentary transverse section correspon-ding generally to Figure 1, but showing a different means of making the mould resilient.

Figure 7 is a transverse section showin a cylinder which has been fully sintered an which has been grooved to relieve from cracking.

Figure 8 is a section corresponding to Figure 7 but showing the grooves as-filled in.

In the drawing similarnumerals indicate like parts.

Sintering, per se, is old and it is also old to sinter linings in furnaces, using magneslte, v'

or other refractory materials such as dolomite, with flux. However, this sintering has to be performed in the difficult conditions and surroundings of intended use, has laid the final surface whichis to be exposed for use last, unevenly and irregularly in many cases, and has permitted no suitable rovision against cracking of the surface ue to temperature changes.

With increasing size and thickness of fur' nace walls, it becomes more and more important to supply sintered bricks or blocks capable ofbeing used as other bricks or blocks are used and to furnishv cylinders, crucibles and other containers,

that, as distinguished from sintering 'in place I pre-form a product or shape by sintering it upon or against a mould or pattern from or parts of containers pre-formed and capable of manwhich it is subse uently removed or which is subsequently bro en from it to free the sintered product.

No attempt has been made to show a complete list of such products or the ways in which my invention may be practiced. I have shown means for moving the product and mould during the sintering operation and an operation intended to be effective upon a stationary product, to indicate that neither the movement nor the stationary character of the parts during operation is essential to the broader features of my invention, and have shown ya complete crucible and partly complete crucible (a cylinder only, lacking a bottom) and a brick for the purpose of indicating that the completeness or lack of completeness of the product as compared with the final container also are not material in the broader aspects of my invention.

In Figures 1 to 3 I have shown my inven- Y tion as applied to the making of a Crucible 10, using a rotatable form or pat-tern 11 upon which yto sinter the Crucible. I prefer to make the form or pattern out of a type of material which will stand the temperature without undue surface shrinkage and .which will be sufficiently yielding and easily destroyed to avoid injury to the product during the sintering or in removal of the pattern.

Because it is desirable to perform the sintering within a furnace Where the heat can be applied to the best advantage Il have shown one for illustratiton which is convenient but not essential. In it provision has also been made for ready introduction of the pattern into the furnace.

This invention is a division of my application magnesite or other materials, Serial N o. 296,803, filed August l, 1928.

The top 12, one end 13, base 14 and side walls l5 are shown as fixed and comprise a casing. The base 14 forms a track for antifriction balls or rollers 16 upon which -is supported the shell 17 of amovable carrier including a refractory Hoor and closing end 18.

The Walls of the furnace are formed of any suitable refractory for which I find dolomite well adapted.

The pattern or mould is shown in Figure l as slittedparallel with the aXis at 19 to increase resilience and compressibility.

Because it is the intention to move the form 11 during sintering and the movement required by the character of product illustrated is rotarial, the pattern is mounted upon a rotatable shaft 20 turning in bearings 21. From this shaft the pattern or mould 11 is supported at intervals by any suitable rods 22.

for sintering refractories from -molten The carrier can be rolled into position within the casino* to completely close the casing, using the fiber 19 as the bottom of the Ythe sides and ends respectively of the product being sintered.

The pattern and mould may be made of any suitable neutral materials of which dolomite is a cheap example but for which graphite is more lasting. I mix it with tar or some similar ingredient which holds the dolomite together and will burn out during sintering or during the pre-heating before so that the mould may be destroyed easily after the sintering of the product has been completed.

Vhe'n the tar-dolomite pattern is in place the furnace is preferably heated preliminarily by flame from an oil or gas burner 26, while the cylinder is turned from time to time, in order to burnout the tar before the sintering begins and to permit a more gradual heating up of the pattern than would take place if the higher temperature of the arc were applied locally at one side or end.

After the cylinder has been heated up by the oil or gas burner it may be further heated by the electric arcs. e

When the pattern is warm enough its movement will be stopped in order that one part of it may be made quite hot. A sintering material such as magnesite or other refractory powder, with a little slag, iron oxide or other flux, will then be spread on the hot place and the heating will be continued until thetest shows that the magnesite has been sintered.

New parts are heated progressively and new, thin layers of the powdered refractory and flux are added about the circumference until a complete cylinder has been formed. The applicationof powdered refractory and flux and heating is progressively continued in layers about the cylinder. Each successive part and layer is fused into homogeneous engagement with its adjacent parts and layers at the sides and beneath it so that when the cylinder is completed it will comprise a homogeneous mass of thoroughly joined fused refractory. f

Where it is desired to facilitate parting from the pattern a. thin parting layer may be .used initially. Various materials are suitable for this purpose such as pure powdered refractory (i. e. lacking a flux) or graphite. Where graphite is used for the mould its material serves this purpose also.

.If a cylinder only be desired the product will now be complete, but if it be desired to apply a bottom, as contemplated in the illustration of Figures 1 to 3, this bottom may be applied by progressive applications of thin layers of refractory fused into position, either after the cylinder has been formed or progressively along with the applications of the layers of the cylinder, the arcs 24 at the end of the pattern being used to perform the sintering end operations.

While I have taken a Crucible as my example and have assumed that it has circular cross-section inside and outside, my method is suited to sinter refractories of all shapes. This apparatus or other apparatus providing movement is suited to sinter fully products of different cross-section, provided:

(a) That the products do not dier too far from true cylinders or other shapes to which the movement has been suited for the heat of the arcs to properly sinter both the nearer and farther parts of the surface during movement of the pattern, or

(b) That the arcs, or pattern, be laterally moved one toward or away from the other at the diderent portions of the pattern so as to maintain the arcs at a suitable sintering distance at all times from the portion of the surface to which the sintered layers is being applied.

The percentage of slag or flux need not be great. Satisfactory percentages of different fluxes are well known. It is desirable to reduce the slag content as the sintering operation proceeds.

While I have illustrated rotary movement only for the. pattern it is evident that my sintering method may be applied to form a sintered product upon a pattern movable according to any other law than that of rotation, the pattern being moved progressively to bring the successive portions of the pattern upon which layers of magnesite and flux have been placed within proper sintering distance of the arcs.

After the operation has been completed the pattern and carrier are removed from the furnace and the pattern or mould is broken out of the crucible leaving the crucible complete and finished with its inner surface composed of the layer of sintered material which was first laid. Because of this fact this inner la er may be more accurately shaped and etter finished than the last laid layers, which would receive the charge if, as previously, the sintering were done in place. My mechanism also makes it possible to pre-form the sintered products at the shop or factory under the most advantageous conditions.

In the form shown in Figures 4 and 5 I show a mould 27 made of a neutral material such as dolomite-tar containing an opening 28 adapted to mould a brick or block or hearth or other shape, for use in building up a refractory lining.

a fixed sintered product pre-formed in a This is intended to represent mould and adapted to form either the whole or a part of a refractory bed or lining. The brick, block, hearth, etc., may be formed Within a furnace of the same character .as that shown in Figure 1 by laying and sintering successive layers of powdered refractory mixed with iux until the product has been completed, after which it is removed from the mould, or the mould is removed from it, so that the product may be shipped for use.

The size of the brick shown is small enough so that it would not be necessary to shift it beneath the arcs for sintering successive layers and the entire area of the brick may be sintered at one time. It will not, therefore, be necessary for the operator to shift the mould longitudinally nor laterally but such movements would be required and can easily be provided for when the product is a large one.

Where the furnace refractories sintered are fairly large there is a tendency of the refractory product to crack in the outer surface. of the refractory, i. e., that farthest removed from the molten metal. I have found thatthis can be relieved greatly by grinding grooves in the refractory at intervals, as shown at 29. The surface tension is relieved by the grinding of these vgrooves and the grooves do not have to go far under the surface to relieve against cracking where there is some tendency to break. I prefer not to leave the grooves open but to lill them in with powdered magnesite which need not be sintered into position.

In the form shown in Figures 4 and 5 it is desirable also to heat up the mould with oil or gas burners, before the arcs are applied, burning out a large part of the tar where this is used, before arc heating for sintering upon or within the mould is begun.

It will be seen that my invention makes up sintered crucibles, cylinders, blocks, etc. free from the difficulties of surroundings and location present where the sintering is done in place, that the surface of the sintered material which is intended to be used may be very exactly predetermined by the contour and iinish of the mould, without the necessity for care in this particular in the manufacture, that the surface intended to be used may be given a finish better than that /Which is left at the back of a sintered wall Where the work is done in place, and'that the mould may be moved as need occurs to easily and conveniently render the whole surface accessible to the greatest extent for the sintering operation.

Such language as has been used as is based upon the mould being insideof the sintered refractory is to be given a meaning to cover a reversal of these positions as the invention will sometimes be applied to sintering within a mould.

This invention makes it possible also alternatively to provide other protection against cracking of the backing of the refractory at the face of the backing.

It is possible to an unusual degree to vary the hardness of the sintered product by use of a. different flux or by varying the percentage of iiux used or by the use of mixed powdered refractories or a different powdered refractory for the final (backing) portion of the sintered refractory which are tougher than those used for the face of the sintered product, or to sinter the outer layers less completely than the inner portion, so as to leave a tougher and less frangible outer layer to protect the outer part of the surface against cracking. v

As will be seen, the protection against cracking by grooving is based upon the idea that the outer surface shall be relieved from circumferential strain due to temperature changes; that the methods by variation of the composition and by difference in extent of sintering are based upon the ideas of toughening the outer layer and altering its surface characteristics to stand the strain and to reduce the frangibility, rather than by increasing the strength to withstand the strain.

In view ofv my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. In a furnace for sintering refractories, furnace walls, a source of heat for the sintering, a pattern and a support for the pattern adapted to move the pattern through a predetermined path suitable for exposing the entire surface of the pattern to be used to the sintering heat.

2. A furnace having walls,

y arc electrodes connected to furnish sintering heat and a rotary support upon which a pattern is mounted so as to expose successive parts of the surface of the pattern to the more intense heat of the arcs formed between the electrodes.

3. In a sintering furnace, a furnace body of refractory, a mould within the body composed of a refractory material capable of withstanding the full sintering temperature interspersed with material adapted to be destroyed by' heat and means for heating the refractory to be sintered upon the surface of the mould.

4. In a sintering furnace, furnace walls, a source of heat for the sintering operation effective within the walls, a pattern located within the walls having an ingredient within the pattern adapted to be destroyed by heat,

a preliminary heater for the furnace and means for rotating the pattern to subject its surface to different sintering temperatures in different positions of the pattern.

5. A sintering furnace made in two parts, one adapted to be fitted within the other, means, carried by one of the parts, for sintering a refractory, a pattern about which the refractory is to be sintered and a mount for the pattern carried by the other part.

6. A sintering furnace made in two one adapted to be fitted within the means, carried by one of the parts for sintering a refractory, a pattern about which the refractory is to be sintered and a revoluble mount for the pattern carried by the other art.

p 7. A sintering furnace made in two parts, one adapted to be fitted within the other, means, carried by one of the parts, for sintering a refractory, a pattern about which the refractory is to be sintered and containing an ingredient adapted to be destroyed by heat and supplemental heating means for the pattern adapted for use in heating the pattern to a predetermined temperature preparatory to centering, the pattern and supplemental means being carried by the second part.

HEINRICH NEUHAUSS.

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